1. Technical Field
The present disclosure relates generally to an apparatus and method for improving the communication quality of a radio and, more particularly, to an apparatus and method for improving the communication quality of a radio, which are capable of smoothly sending and restoring user voice data even when it is difficult for a reception-side radio to normally receive the user voice data due to a transmission error attributable to a high bit error in a channel upon making voice communication using a radio over a poor-quality radio channel, such as a short-wave channel.
2. Description of the Related Art
Radios (Walkie-talkies, Two-way radios) were first developed in the early 1940's, and started to be used in the military and in industrial fields in various manners from the Second World War.
In general, radios can directly communicate with each other without requiring a separate system, such as a base station. Since one-to-many communication can be performed using radios, radios are widely used in operating environments requiring command and control, such as in the military or in industrial fields.
Radios using an analog method were used in the past, but recently radios using a digital method are commonly used in line with the advancement of communication technology. Radios may be basically classified into radios for a high frequency (HF) channel, radios for a very high frequency (VHF) channel, and radios for an ultra-high frequency (UHF) channel depending on the frequency bands used.
In the case of a short-wave channel, a change in channel is considerable depending on the time at which communication is performed and the place in which communication is performed, and there is the case where a bit error rate (BER) increases to a 10−2 level at which it is almost impossible to perform voice communication using an analog method-based radio.
For example, Korean Patent Application Publication No. 10-2011-0121675 entitled “Communication Bluetooth System” discloses a method of controlling input voice in order to provide PTT service, such as that of a radio, in a mobile communication terminal.
In a radio channel to which such a radio communication device is applied, when data is sent over the channel, an error inevitably occurs due to noise, interference, and fading depending on channel conditions, and loss of data occurs due to the generated error. In order to reduce the loss of data attributable to the occurrence of the error on the reception side as described above, various error control methods are used in a modem depending on the characteristics of a channel.
In the case of a short-wave channel, a change in channel is considerable depending on the time at which communication is performed and the place in which communication is performed, and there is the case where a BER increases to a 10−2 level at which it is almost impossible to perform voice communication using an analog method-based radio.
In order to perform voice communication even over such a poor channel, a voice encoder for high compression of a user voice signal at a low transfer rate of 1,200 bps, or 600 bps lower than 2,400 bps, and a military standard modem optimized for a corresponding channel have been applied to some military radios. For example, a minimum level of voice communication can be performed using a digital method of combining a military vocoder having a transfer rate of 600 bps and a modem having a transfer rate of 600 bps even in a channel environment in which a channel error is at a high level, such as a BER 10−2 level.
If a voice signal is encoded at a low transfer rate of 2,400 bps or less as described above, communication quality is inevitably deteriorated upon restoration of the voice on the reception side due to loss of the voice signal in the encoding process. In particular, in the case of a current 600-bps vocoder, a large amount of information is lost in a voice signal due to high compression upon encoding a voice, and communication quality is considerably deteriorated on the reception side upon restoring and listening to voice. As a result, smooth communication is limited due to transmitted voice having poor articulation.